Hoarfrost Castle is a user created plugin for the fourth game in The Elder Scrolls series, Oblivion. This is a series of quests that at the end result in the player owning a castle with numerous benefits. Unlike the official residences that are available in the game, this doesn't require either purchasing or having to buy stuff to furnish it. Instead, the player gets Hoarfrost Castle and its benefits by completing a series of quests.
If you agree to help, he gives you the Hoarfrost Castle Key which opens the door to the Great Hall. If you decline, you can always come back later and accept.
"I have met with Ignatius Essagan, Steward of Hoarfrost Castle; and now sole owner, following the recent massacre of the Callonus family who lived there previously. He has, in turn, offered ownership of the castle to me; if I can rid the keep of the undead host that has taken up residence. I have accepted his generous offer. Ignatius says the revenants came up from the cellar - so that might be a good place to investigate. Perhaps I can discover where they got in."
There isn't a great deal in here. There are three more Zombies in the Sleeping Quarters, and another in the Mage's Study, which also contain a couple of items of alchemical equipment, a lot of low value books, some ingredients, a jewellery box and a locked chest. The exits to the outside from the Sleeping Quarters and Mage's Study are all locked and need keys to open. The key is the Hoarfrost Castle Key, so you can leave by these doors if desired.
Once you defeat the lich, your log updates again.
"I destroyed the lich beneath Hoarfrost Castle, and felt a thrum of energy pass through the air as it fell. I wonder what it could mean? In any case, I should probably check its body, before returning to Ignatius to let him know what happened..."
If you didn't kill any of the undead in the Keep, they are now all gone. Once you exit the Keep, your log updates again.
"Hoarfrost Keep was empty of the undead that filled it earlier. Maybe destroying their lich master served to drive them away. I have done what Ignatius asked; hopefully he will be satisfied with my account."
Speak to Ignatius. He asks you to confirm that the lich is, indeed, dead, and after doing so says that he will fulfil his promise and that Hoarfrost Castle is now yours. He will once again take up residence in the castle and now that he has access to the castle funds again he can pay to get it repaired. This will be done by magic, will take three days, and during the repair you won't have access to it.
Because the repair of the castle will mean the disposal of all the contents of the keep, he asks you to confirm that you want the work to start now, and says you should remove anything you want to keep, as otherwise it will be discarded. Once you confirm the repairs should go ahead, both the Hoarfrost Castle Key and Master Bedroom Key are removed from your inventory. Ignatius tells you to return in three days and your log updates.
Once the repairs are finished, your quest log updates informing you of this. Return to the castle when ready and speak to Ignatius again, who is still outside the gate. Ignatius says he was waiting for you to return before going back into the castle. He gives you a scroll called Hoarfrost Castle Particulars which details what is available in the castle and what still needs doing.
Ignatius then returns to the castle and says to you to speak to him when ready. He rooms in the east wing, but can be found around the castle. Explore the castle if you like; everything has been repaired and there is plenty of storage space.
When you speak to him again, this finishes the Hoarfrost Castle quest. The quest Tithes and Tribulations can now be started.